Imiquimod, 1-isobutyl-1H-imidazo[4,5-C]quinolin-4-amine, is an immune response modifier, useful for treating viral infections, such as genital warts. Imiquimod is disclosed in U.S. Pat. Nos. 4,689,338 and 5,238,944 and has the structure:

Several methods are known in the art for making 1H-imidazo[4,5-c]quinoline 4-amines, including Imiquimod. The amino group in the 4 position has been introduced in essentially three ways: The first is by nucleophilic substitution of a leaving group, e.g., Cl, triflate, etc., with ammonia, dibenzylamine or an azido group; the second is by reacting 1-isobutyl-1H-imidazo[4,5-c]quinoline-N-oxide with ammonium hydroxide or ammonium salts in the presence of tosyl chloride at 0–5° C.; and the third is by reacting 1-isobutyl-1H-imidazo[4,5-c]quinoline-N-oxide with benzoyl isocyanate.
Nucleophilic substitution reactions are disclosed in, for example, WO 97/48704, WO 92/06093, U.S. Pat. Nos. 5,395,937, 5,756,747, 4,988,815, 5,602,256, 5,578,727, 4,698,348, 4,689,388, European patents EP 145340, EP 0385630, EP 310950 and JP 04193866. Specifically, in WO 97/48704 the amino group is introduced by reaction of a 4-chloro derivative with sodium azide to obtain a tetrazole moiety. Reaction of the tetrazole moiety with triphenylphosphine gives the 4-amino derivative. In U.S. Pat. No. 5,395,937, a 4-triflate derivative is reacted with dibenzylamine. The catalytic reduction of the 4-dibenzylamino derivative places an amino group in the 4-position. U.S. Pat. No. 5,756,474, discloses a nucleophilic substitution with ammonia on a 4-chloro derivative, obtained by isomerization of 1-isobutyl-1H-imidazo[4,5-c]quinoline-N-oxide to the 4-hydroxy derivative, followed by reaction with POCl3. The following patents all disclose a nucleophilic substitution of 1-isobutyl-1H-imidazo[4,5-c]quinoline-4-chloro with ammonia at high temperature and pressure: U.S. Pat. Nos. 4,988,815, 5,602256, 5,578,727, 4,698,348, 4,689,388, EP 145340, JP 04193866, EP 0385630, and EP 310950.
WO 92/06093 discloses reacting 1-isobutyl-1H-imidazo[4,5-c]quinoline-N-oxide with ammonium hydroxide or ammonium salts in the presence of tosyl chloride at 0–5° C.
WO 92/15581 discloses reacting 1-isobutyl-1H-imidazo[4,5-c]quinoline-N-oxide with benzoyl isocyanate.
However, a need exists in the art for making 1H-imidazo[4,5-C]quinoline 4-amines, especially Imiquimod, in high purity and high yield and which does not require high temperature or pressure.